1. Field of the Invention
The present invention relates to an apparatus for processing a substrate for a semiconductor wafer or a LCD(Liquid Crystal Display), and in particular to a gas distributor for the above-described apparatus.
2. Description of the Background Art
A semiconductor device or LCD is fabricated by repeatedly performing a process for forming a thin film on a semiconductor wafer or LCD substrate and etching a part of the thin film.
Therefore, the thin film formation process and etching process are important processes for fabricating the semiconductor device and LCD. As a representative method for forming the above-described thin film, a CVD(Chemical Vapor Deposition) method is known, and as a process for etching the thin film, a RIE(Reactive Ion Etching) method is known.
In the chemical vapor deposition process and active ion etching process, a certain gas is filled in the process chamber. A chemical reaction between gases or a chemical reaction between a wafer in the reaction furnace or a substrate material and the gas is performed. Therefore, in the chemical vapor deposition apparatus or active ion etching apparatus, a gas distributor which is capable of uniformly distributing in the direction of a certain destination, namely, the wafer or the substrate at a certain speed and under a pressure is used. The present invention relates to the above-described gas distributor.
In particular, in the chemical vapor deposition apparatus, the gas distributor is an important element for obtaining a good quality thin film which has a uniform thickness on the semiconductor wafer or LCD substrate and does not contain particles. The following conditions are required.
Namely, first, gas must be uniformly distributed over the wafer or substrate, and second, a chemical reaction should be stably performed in the interior of the gas distributor or on the outer surface by obtaining or maintaining an activated energy of the gas before the gas is distributed in the direction of a work stand, on which the wafer is placed, from the gas distributor or after the gas is distributed. Namely, the reaction is guided to occur on a destination material, namely, on the wafer.
In particular, in the MOCVD(Metal Organic Chemical Vapor Deposition) method for depositing the organic metal thin film which is widely used, the temperature stability and uniformity of a source gas are affected by the characteristic of the thin film. However, in the gas distributor of the chemical vapor deposition apparatus which is widely used, it is difficult to obtain a good quality film.
FIG. 1 is a cross-sectional view illustrating the interior of a reaction furnace of the conventional chemical vapor deposition apparatus. As shown therein, the reaction furnace is surrounded by a cylindrical outer wall 10, and a gas distributor 11 is installed at an upper portion of the cylindrical outer wall 10, and a gas outlet tube 15 is provided at the bottom. A gas inlet tube 12 is provided on the upper surface of the gas distributor 11 through which gas is introduced. A work stand 13 is placed in the interior of the reaction furnace surrounded by the outer wall 10 and below the gas distributor 11. A wafer W is placed on the upper surface of the work stand 13, and a heating apparatus 14 is installed below the work stand. A gas outlet portion 15 is connected at the lower surface of the reaction furnace outer wall 10 for exhausting gas after the reaction is completed.
The principle for forming a thin film on the wafer W using the chemical vapor deposition apparatus of FIG. 1 will be explained. Namely, a source gas or process source is flown into a vaporizer(not shown) in a fluid state for forming a thin film. The thusly flown source gas or process source is mixed with a carry gas formed of N2, O2, Ar, etc. in the vaporizer and is vaporized. Next, the vaporized process source is flown into the gas distributor 11 via the gas inlet port 12 in a gas state and reaches at the wafer via a plurality of nozzles 11a formed at the gas distributor 11 and is chemically reacted based on a heat energy generated by the heating apparatus 14, so that a thin film is formed on the wafer W. At this time, if a heat environment is not proper in the interior of the gas distributor 11, the process gases may be abnormally reacted or the vaporized gas may be liquefied, so that the thin film formed on the wafer W includes particles, whereby the quality of the film may be decreased, and it is impossible to obtain a certain deposition ratio. Therefore, in order to prevent the above-described problems, the temperature in the gas distributor is maintained at a certain degree.
The structure of the conventional gas distributor and the temperature control method will be explained.
FIG. 2B is a cross-sectional view illustrating a conventional first type gas distributor 20. As shown therein, the gas distributor 20 includes an upper plate 21 and a multiple-hole plate 23 having a plurality of holes or nozzles 22. A gas inlet tube 24 is connected to a center portion of the upper plate 21. The upper plate 21 and the multiple-hole plate 23 are engaged by a plurality of screws 26 along an edge portion. In addition, a heater 25 is installed at an edge portion of the upper plate at an angle of 90xc2x0. FIG. 2A is a plan view illustrating the upper surface of the first type gas distributor of FIG. 2B. As shown therein, four heaters 25 are installed at an edge portion of the upper plate 21, and a gas inlet tube 24 is connected to a center portion of the upper plate 24.
FIG. 3A is a vertical cross-sectional view illustrating a conventional second type gas distributor. As shown therein, a gas distributor 30 includes an upper plate 31, and a multiple-hole plate 33 having a plurality of holes or nozzles 32. A gas inlet tube 34 is connected to a center portion of the upper plate 31, and the upper plate 31 and the multiple-hole plate 33 are engaged by a plurality of screws 36 along an edge portion. Four heaters 35 are installed at a center portion of the upper plate 31 near the gas inlet tube 34 at a certain interval. The position of the heater is different compared to the first type gas distributor. Namely, the first type heater is formed at an edge portion of the upper plate, and the second type heater is formed at a center portion of the upper plate.
FIG. 3B is a plan view illustrating a second type gas distributor of FIG. 3A. The same elements as FIG. 3A are given the same reference numerals. A gas inlet tube 34 is installed at a center of the upper plate 31, and a heater 35 is installed around the gas inlet tube 34.
FIG. 3C is a plan view illustrating a multiple-hole plate 33 of the second type gas distributor of FIG. 3A. A plurality of nozzles 32 each having a diameter of 1xcx9c2 mm are installed at a certain distance from one another. A plurality of screw holes 36a are formed at an edge portion of the multiple-hole plate 33 for receiving the screws therein.
FIG. 4A is a vertical cross-sectional view illustrating a third type gas distributor 40. As shown therein, the third type gas distributor 40 includes an upper plate 41, a multiple-hole plate 43 having a plurality of nozzles 42, a gas inlet tube 44, and a flat plate heater 45. The upper plate 41 and the multiple-hole plate 43 are engaged by the screws 46. The plate heater 45 is installed on the entire upper portion of the upper plate 41. The multiple-hole plate 43 is formed in a dish shape and has a distributing function capable of distributing a certain gas to an outer portion in the chamber. The multiple-hole plate 43 includes a lower portion 43a and a slant portion 43b. 
FIG. 4B is a plan view illustrating a third type gas distributor of FIG. 4A. The same elements as FIG. 4A are given the same reference numerals. FIG. 4C illustrates a multiple-hole plate 43. In FIG. 4C, the same reference numerals of FIG. 4C as FIG. 4A correspond to the same elements of FIG. 4A.
The operation of first through third type conventional gas distributors will be explained.
In the first and second gas distributor, a vaporized fluid state gas flown onto the upper plate of the gas distributor via the gas inlet tubes 24 and 34 is heated by four stick-shaped heaters arranged on the upper plate and has a certain degree temperature. The thusly flown gas is uniformly distributed onto the wafer or substrate in the chamber via the nozzles of the multiple-hole plate.
In the third type gas distributor, a slant portion having a slanted degree of about 30xc2x0 with respect to the horizontal surface at the outer portion of the multiple-hole plate for supplying gas to the edge portion of the wafer or substrate.
The above-described conventional first through third gas distributors have the following problems.
In the first type gas distributor, since the heat is performed by a stick heater installed at an outer portion of the upper plate, the heat is not uniformly transferred to the gas furnace for thereby decreasing a uniformity of the gas temperature. Therefore, the thickness of the film formed on the wafer is not uniform. In addition, it is difficult to obtain a film having a uniform composition, so that a film growth efficiency is decreased. Since the nozzle of the multiple-hole plate is a linear type, a vortex flow is formed at the gas outlet portion of the nozzle. Since the distribution range is small, the gas reaction effect is decreased. In addition, the outer portion becomes a dead space, the particles may be formed. The second type gas distributor has the same disadvantages as the first type gas distributor.
In the third type gas distributor, since the gas is distributed toward the wall of the chamber via the slant portion of the multiple-hole plate, so that the distribution loss of the source gas is increased. At the slant portion, the gas flow is bad. Since the nozzle wall is linear, the particles may be formed. Since the outer portion of the multiple-hole plate directly contacts with the plate heater, the heat is directly transferred from the heater. Since the center portion of the multiple-hole plate is heated by a radiant heat from the plate heater, a non-uniformity of the film thickness occurs due to a difference between the temperature of the gas flowing via the nozzle installed at the center portion of the multiple-hole plate and the temperature of the gas flowing via the nozzle at the edge portion of the multiple-hole plate.
Accordingly, it is an object of the present invention to provide a temperature controllable gas distributor which is capable of obtaining a good quality thin film and increasing a thin film deposition ratio by preventing an earlier reaction in the interior of the gas distributor and a liquefaction of the vaporized gas.
It is another object of the present invention to provide a temperature controllable gas distributor which is capable of distributing a thermally stable gas for obtaining a uniform thickness of a thin film.
It is another object of the present invention to provide a temperature controllable gas distributor which is capable of preventing a particle formation and forming a good quality thin film by improving a linear type nozzle and providing different diameters of upper, intermediate, and lower portions.
To achieve the above objects, there is provided a temperature controllable gas distributor wherein a cover is formed of an upper cover and a lower cover which are welded in such a manner that a first passage is formed between the upper and lower covers for flowing fluid therethrough, and first and second temperature detectors(thermo couplers) are installed in the first passage for detecting a fluid temperature, and an inlet tube for flowing the fluid into the first passage and an outlet tube for flowing the fluid from the first passage to the outside of the cover are formed in the first passage so that the fluid flows the upper cover, and a plurality of nozzles are formed on the distributor plate in such a manner that the gas flows through the distributing plate, and a third passage is formed on the distributor plate for flowing fluid, and the third passage is connected with the fluid inlet tube and the fluid outlet tube.
In the temperature controllable gas distributor according to the present invention, a second passage is formed along an edge portion of an upper cover, and an electric heat wire for the heat is installed at a second passage.
In the temperature controllable gas distributor according to the present invention, an electric heat wire for the heat is installed at a third passage of a distributor plate.
In the temperature controllable gas distributor according to the present invention, the upper portion diameter, intermediate portion diameter and lower portion diameters of the nozzle are different, and the upper portion diameter is largest, and the lower portion diameter is smallest.
Additional advantages, objects and features of the invention will become more apparent from the description which follows.